WORKING PRINCIPLE OF DOWNHOLE FISHING TOOLS

Working principle of short fish top overshot:

After entering the fish, first push the slips up to release the spiral cone, then the slips will swell and the fish top will enter. When lifting and pulling the drilling tool, the barrel will go up, the two spiral cones will fit, the slips will bite into the fish, and the clamping force will increase with the increase of lifting force to realize fishing. Once the fish needs to exit the tool in case of jamming, add the following striking force to the fishing barrel to make the basket slips and the spiral cone of the barrel detached, and then run the right-hand drilling tool and lift it up. There is a positive torque between the inner diameter of the spiral slips and the fish head, forcing the slips to be in the state of loose and swollen, preventing the fitting of the spiral cone surface, and the tool is withdrawn.

Working principle of retractable overshot:

When the fish is caught by the retractable slip fishing barrel, the drilling tool is lifted up, and the spiral serrated conical surface outside the slip has relative displacement with the corresponding tooth surface inside the barrel, and the fish is clamped and fished out.

Working principle of slip overshot:

When the guide shoe of the tool is introduced into the fish, lower the drilling tool, and the fish will push the slips upward, compress the spring, so that the slips can be detached from the taper hole of the cylinder and gradually separate, and the fish will enter the slips. At this time, the slips will be pressed under the spring force, hold the fish top, and give the fish top the initial clamping force. Lift up the drilling tool. Under the action of the initial clamping force, the barrel moves upward, the slips and the inner and outer conical surfaces of the barrel fit together to produce a radial clamping force, so as to block the falling fish and pull out the drill.

For the fish with different diameters, the fish with different sizes can be salvaged by changing different slips with the permission of the barrel.

Working principle of retractable spear:

1. Salvage

In the free state, the outer diameter of the circular slip is slightly larger than the inner diameter of the falling object. When the tool enters the fish cavity, the round slips are compressed to produce a certain external expansion force, which makes the slips close to the inner wall of the falling object. With the rising of the mandrel and the increasing of the lifting force, the serrated threads on the mandrel and slip fit each other, and the slip produces radial force, which makes it catch the fish and realize fishing.

2. Quit

Once the fish is stuck and can't be fished out and needs to exit the spear, as long as a certain down force is given to the mandrel, the circular slip and the internal and external serrated threads of the mandrel can be disengaged, and then the drilling tool can be turned forward for 2-3 turns, and the relative displacement between the circular slip and the mandrel will be generated, which will cause the circular slip to move downward along the serrated thread of the mandrel until the circular slip contacts the upper end face of the release ring, and then the drilling tool can be pulled up and out Drop fish.

Working principle of coupling spear:

The coupling spear is actually a kind of fishing tool with internal and external threads. In order to make the coupling spear enter the coupling, the slip has several grooves along the longitudinal direction, and each groove is a slip, which enters the coupling buckle according to its elastic deformation. It also relies on the radial expansion force after the core shaft and the internal and external cone surfaces of the slip fit to maintain the connection performance after the buckle, so as to catch the fish.

Working principle of slide slip spear:

The slide slip spear refers to one of the spear fishing tools used in drilling operation. When the spear and slips enter the fish cavity, the slips slide down by their own weight, and the slips displace relative to the inclined plane. The distance between the slip tooth surface and the spear centerline increases, so that the fishing size increases gradually until it contacts the inner wall of the fish cavity. When the spear is lifted, the radial force generated by the upward movement of the inclined plane forces the slips to bite into the inner wall of the falling object and catch the falling object.

Working principle of die collar:

The working principle of die collar is the same as that of the male cone, which relies on the fishing thread to make a thread on the outer wall of the falling object under the pressure and torque of the drilling tool, so as to remove the falling object. As far as the mechanism of buckle making is concerned, it belongs to extrusion feeding and does not produce chips.

Working principle of taper tap:

When the tap enters the inner hole of the fishing object, add appropriate WOB and rotate the drilling tool to force the fishing thread to squeeze into the inner wall of the fish to make the thread. When the buckle can bear certain tension and torque, it can be lifted up or reversed to pull out all or part of the falling objects.

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